Pneumatic hammers or breakers are used for breaking road pavement, such as concrete, asphalt, and the like ground materials. Such hammers generally consist of a tubular member having a bottom drill bit. Each hammer may be operated by a single man, either directly with both hands controlling the top transverse handle bar thereof, or indirectly via a tractor monitoring the hammer via a boom and hammer mount. These devices being potentially dangerous (for the arms, legs and feet of the worker) and generating heavy vibrations and high level of sound, they are less used directly by a man because of health considerations and also because they are time consuming. As for known machine operated hammers, the machine mounts are all fixedly mounted to the hammer bodies so that the machine boom will "push" the hammer to the ground; such pushing has a tendency of rendering the hammer a crude tool, i.e. that one cannot do precision work therewith and thus can damage a pavement layer not intended to be broken.